class Solution
{
public:
    int longestCommonSubsequence(string s1, string s2)
    {
        int m = s1.size(), n = s2.size();
        s1 = " " + s1, s2 = " " + s2;
        vector<vector<int>> dp(m + 1, vector<int>(n + 1));

        for (int i = 1; i <= m; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                if (s1[i] == s2[j])
                    dp[i][j] = dp[i - 1][j - 1] + 1;
                else
                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
            }
        }

        return dp[m][n];
    }
};